2018-05-30

binary stars, spectroscopic parallaxes. planets

Andy Casey (Monash) is in town to work on Gaia DR2 and he has been looking at using the radial-velocity uncertainty (which, in the database, is really an empirical scatter across measurements) to identify binary stars. This is a great idea. I was pitching various ways to calibrate this quantity to make it more reliable and then he reminded me that many binaries have tens of km/s semi-amplitudes! Duh. The signal is super-strong. This is a great #GaiaSprint project!

Christina Eilers (MPIA) and I had success today on spectroscopic parallaxes for stars at the top of the red-giant branch: We are now able to predict absolute luminosities (and therefore parallaxes) with almost 10-percent accuracy! That makes them only slightly worse than red-clump stars, and we think there is more information to exploit in the data. Our method is a bit hacky: We are still using spectroscopic quantities from the APOGEE pipelines and not just the spectra themselves, but it should point the way to a cleaner method soon.

Stars Meeting at Flatiron was a great success. One exciting project in progress is that Ruth Angus (Columbia) is finding relationships between exoplanet occurrence and host-star orbital actions! Now the causal part: Is this because of age or abundances or dynamical interactions? Another is that Ben Montet (Chicago) proposed that we find non-transiting hot-jupiter exoplanets by looking at surface rotation: There is at least weak evidence that stars with hot jupiters spin faster—or appear to. That's exciting as another possible indirect planet-detection technique.